Organic Light Emitting Display (OLED) has self-luminous, low driving voltage, high luminous efficiency, short response time, sharpness and contrast, nearly 180° viewing angle, wide temperature range, flexible, large-area panchromatic and many other advantages, which is recognized as the most promising display device in the field.
OLED can be classified into passive matrix OLED (PMOLED) and active matrix OLED (AMOLED) according to the driving mode, that is, direct addressing and thin film transistor (TFT) matrix addressing. Among them, AMOLED has a matrix arrangement of pixels, belonging to the active display type with high luminous efficiency, is usually used for high-definition large-size display device.
OLED device usually includes a substrate, an anode provided on the substrate, a hole injection layer provided on the anode, a hole transport layer provided on the hole injection layer, a light emitting layer provided on the hole transport layer, an electron transport layer provided on the light emitting layer, and a cathode provided on the electron transport layer. The principle of light-emitting OLED display device is that the semiconductor material and organic light-emitting material under an electric field driven through a carrier injection and a recombination led to light. Specifically, OLED display device generally adopts an ITO pixel electrode and a metal electrode respectively as the anode and the cathode of the device. Under a certain voltage, the electron and hole are injected from the cathode and the anode into the electron transport layer and the hole transport layer respectively. The electron and hole migrate to the light-emitting layer through the electron transport layer and the hole transport layer, respectively, and meet in the light-emitting layer to excite a light-emitting molecule, which emits visible light through radiation relaxation.
Large-size OLED panels work differently because their cathodes have larger resistances and produce different IR drops at different positions, resulting in uneven brightness of the OLED panel. Therefore, an additional connection to the cathode is required, such that the voltage is applied to the cathode through the auxiliary electrode to solve the problem of display unevenness caused by the IR voltage drop of the cathode and make the display of the OLED panel uniform and stable. In the prior art, a pillar having an inverted trapezoid in longitudinal section is generally fabricated on the OLED panel to achieve the connection between the auxiliary electrode and the cathode. The isolation column has less selectivity of raw materials, increases the cost of the OLED panel. The fabrication process of the panel is therefore complicated, especially for the OLED panel fabricated by the inkjet printing (IJP) method, the process of manufacturing the isolation column is more difficult to realize.